The field of endoscopic surgery has been advancing rapidly in recent years. In this form of surgery, procedures are performed inside the body of a patient using instruments inserted through small incisions or ports in the body. The surgery is performed with the aid of an endoscope, which is a thin, tube-like instrument featuring a light source, a viewing lens, and/or various other attachments such as irrigators, scissors, snares, retractors, or forceps.
This form of surgery allows internal visualization of the body structure without the necessity of excessive dissection of tissue. Typical endoscopes often are in the 5-12 mm diameter range and thus require only very small incisions to insert them into the body. Endoscopic surgery has developed rapidly because of the numerous benefits arising in favor of the patient. Since there is only a small incision to permit entrance of the endoscope, endoscopic surgery results in less trauma to the body and faster patient recovery.
Electrosurgery has been an accepted surgical tool for at least six decades. The use of an electric current to control bleeding, known as "electrocautery", replaced thermal cautery because of its speed and effectiveness. Electrocautery is based on the observation that a high frequency alternating current can be passed through the body with no untoward effects other than heat production. Use of an intermittent high frequency current results in blood coagulation within tissues with little or no cutting effect on the tissues themselves.
Electrosurgical devices can be monopolar or bipolar. In a monopolar system, the electrical current passes from a smaller "active" electrode located at the tip of the device, through the tissue, to a dispersive electrode, also known as a patient plate. The dispersive electrode has a large contact area. Because of its broad exposure area, temperature rise is insignificant. In contrast, the active electrode is typically 1 mm in size, thus concentrating the dissipated electrical current to a highly confined region with a resulting rapid rise in tissue temperature.
Electrosurgery performed in open, that is, non-endoscopic surgery is associated with significant hazards. These include the risk of explosive anaesthetic agents, or flammable bowel gas, faulty grounding contacts, or short circuiting. One of the hazards frequently associated with the use of monopolar electrosurgery is the inadvertent reduction of area at the dispersive electrode, which has resulted, in some cases, in severe burns to the patient's body.
Many of these grounding plate and non-conductive tissue thermal injuries are thought to be reduced by the use of bipolar cautery. With bipolar cautery, both the active and ground electrodes are placed at the tips of the forceps, and thus current flows only between the two active electrodes.
This bipolar method, however, has a number of significant disadvantages. These include tissue dehydration, increased resistance, and uncontrolled heating, leading to tissue vaporization, charring, and actual explosions. A major disadvantage is the rapid heating, burning, and sticking of tissue. This results in the need for frequent cleaning of the bipolar forceps, which slows the operation, and in fact, results in ineffective and inefficient coagulation. In addition, when tissue adheres to the tips of the forceps, withdrawal of forceps from the coagulated tissue can cause inadvertent tearing and hemorrhaging.
Stainless steel has been the metal of choice for the production of both monopolar and bipolar coagulation forceps. Steel, however, is a poor thermal conductor, and its use results in uncontrolled heating at the tips of the forceps and adhesion of tissue. Attempts to prevent adhesion have included various coatings of the stainless steel forceps, but these attempts have not been successful.
The techniques of endoscopic surgery and electrocautery have been combined, resulting in endoscopic devices capable of coagulating tissue. However, additional disadvantages arise during endoscopic procedures because the electrocauterization is done inside the patient's body through an endosurgical port, with no direct access by the surgeon to the site of the procedure. The forceps must be cleaned outside the patient's body, or through the use of a separate device inserted into the body. This slows the procedure and increases trauma to the patient.
Bipolar coagulation has never been completely accepted by surgeons practicing laparoscopic surgery, that is, endoscopic surgery within the abdominal cavity. The monopolar coagulating electrode is considered to be the optimal tool, but its use is complicated by inadvertent injury to the bowel or adjacent structures by short circuiting, as well as tissue oxidation and adherence to the monopolar tips. In addition, the use of monopolar endoscopic electrocautery devices can interfere with radio-frequency waves which are often used to assist the surgeon in visualizing internal body structures.
There is therefore a need for a bipolar coagulation device suitable for use in laparoscopic and other forms of endoscopic surgery, capable of disseminating heat away from the tips of the forceps to reduce uncontrolled heating, charring and sticking of the tissue during surgery, and a mechanism for cleaning the tips of the forceps quickly and easily during the endoscopic procedure.